Mill vise clamps. By Jon's Workshop.
37:13 video:
https://www.youtube.com/watch?v=3EANHl68WKA
50:06 video:
https://www.youtube.com/watch?v=d5I7NmQRYhU
(Note: Like many of the other videos I post, this is not my build. I'm adding this comment here because, coincidentally, my name is Jon and the builder's name is Jon's Workshop.)